Electronics (Mike Jaroch)


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D

D'ARSONVAL METER MOVEMENT

The permanent-magnet moving-coil movement used in most meters [3] [16].


DAMPED WAVE

A sinusoidal wave in which the amplitude steadily decreases with time. Often
associated with energy loss [9].


DAMPING

(1) The process of smoothing out oscillations. (2) In a meter, this process is used to keep the pointer of the meter from overshooting the correct reading [3]. (3) A mechanical or electrical technique used in synchro receivers to prevent the rotor from oscillating or spinning. Damping is also used in
servosystems to minimize overshoot of the load [15] [16].


DATA PROCESSING

The execution of a systematic sequence of operations performed upon data.
Synonymous with information processing [13].


DATA TRANSMISSION

The transfer of information from one place to another or from one part of a
system to another [15].


dBm

An abbreviation used to represent power levels above or below a 1-milliwatt reference [16].

DEAD SHORT

A short circuit having minimum resistance [1].

DECIMAL

Pertaining to the number representation system with a radix of ten [13].

DECIMAL DIGIT

In decimal notation, one of the characters 0 through 9 [13].

DECIMAL NOTATION

A fixed radix notation where the radix is ten [13].

DECIMAL NUMERAL

A decimal representation of a number [13].

DECIMAL POINT

The radix point in decimal representation [13].

DECOUPLING CAPACITOR

A capacitor used to transfer unwanted signals out of a circuit; for example, coupling an unwanted signal to ground. Also called a BYPASS CAPACITOR [8].


DEFLECTION COILS

In a cathode-ray tube, coils used to bend an electron beam a desired amount [18].

DEFLECTION PLATES

Two pairs of parallel electrodes, one pair set forward of the other and at right
angles to each other, parallel to the axis of the electron stream within an electrostatic cathode-ray tube [6].


DEGENERATION

The process whereby a part of the output signal of an amplifying device is returned to its input circuit in such a manner that it tends to cancel part of the input [7].


DEGENERATIVE FEEDBACK

Feedback in which the feedback signal is out of phase with the input signal; also called NEGATIVE FEEDBACK [8].


DEGREE-OF-FREEDOM

The number of axes about which a gyro is free to precess [15].

DEIONIZATION POTENTIAL

The potential at which ionization of the gas within a gas-filled tube ceases and conduction stops; also referred to as extinction potential [6].


DEIONIZATION TIME

In a spark gap, the time required for ionized gas to return to its neutral state
after the spark is removed [18].


DELTA

A three-phase connection in which windings are connected end-to-end, forming a closed loop that resembles the Greek letter delta. A separate phase wire is then connected to each of the three junctions [5].


DEMODULATION

The removal of intelligence from a transmission medium [12].

DEMODULATOR

A circuit used in servosystems to convert an ac signal to a dc signal. The magnitude of the dc output is determined by the magnitude of the ac input signal, and its polarity is determined by whether the ac input signal is in or out of phase with the ac reference voltage [15].


DeMORGAN'S THEOREM

A theorem which states that the inversion of a series of AND applications is
equal to the same series of inverted OR applications, or the inversion of a series of OR applications is equal to the same series of inverted AND applications.


DENSITY

(1) The compactness of a substance. (2) Mass per unit volume [10].

DEPLETION REGION

The region in a semiconductor where essentially all free electrons and holes
have been swept out by the electrostatic field which exists there [7].


DEPOT-LEVEL MAINTENANCE (SM&R CODE D)

Supports SM&R Code I and SM&R Code O activities through extensive shop facilities and equipment and highly skilled personnel [14].


DESIGNATION

Operational phase of a fire-control or track radar during which the radar is directed to the general direction of a desired target [18].


DETECTION

The separation of low-frequency (audio) intelligence from the high-frequency carrier [17].

DETECTOR

A mixer or converter in a superheterodyne receiver [18].

DICE

Uncased chips [14].

DIE BONDING

Process of mounting a chip to a package [14].

DIELECTRIC

An insulator; a term applied to the insulating material between the plates of a capacitor [2].


DIELECTRIC CONSTANT

The ratio of a given dielectric to the dielectric value of air [2] [11].

DIELECTRIC FIELD

The space between and around charged bodies in which their influence is felt.
Also called ELECTRIC FIELD OF FORCE or an ELECTROSTATIC FIELD [1].


DIELECTRIC HEATING

The heating of an insulating material by a high-frequency electric field [10].

DIELECTRIC HYSTERESIS LOSS

Power loss of a capacitor because of the changes in orientation of
electron orbits in the dielectric; the changes in orientation are caused by rapid reversal in polarity of line voltage. The higher the frequency, the greater the loss [2].


DIELECTRIC LEAKAGE

Power loss of a capacitor because of the leakage of current through the
dielectric. Also relates to leakage resistance; the higher the leakage resistance, the lower the dielectric leakage [2].


DIELECTRIC LOSSES

The losses resulting from the heating effect on the dielectric material between
conductors [10] [11].


DIELECTRIC STRENGTH

The ability of an insulator to withstand a potential difference without
breaking down (usually expressed in terms of voltage) [4].


DIFFERENCE FREQUENCY

See BEAT FREQUENCY [18].

DIFFERENCE OF POTENTIAL

A voltage between two points [6].

DIFFERENTIAL AMPLIFIER

A circuit that amplifies the difference between two input signals [8].

DIFFRACTION

The bending of waves (as light or RF) when the waves are met with some form of obstruction [10].


DIFFUSION

(1) The scattering of reflected light waves from an object, such as white paper [10]. (2) Controlled application of impurity atoms to a semiconductor substrate [14].


DIGIT

A symbol that represents one of the nonnegative integers smaller than the radix. For example, in decimal notation a digit is one of the characters from 0 through 9 [13].


DIGITAL COMPUTER

(1) A computer in which discrete representation of data is used. (2) A computer
that operates on discrete data by performing arithmetic and logic processes on these data [13].


DIODE

An electron tube containing two electrodes: a cathode and a plate [6]. (2) A two element, solid-state device made of either germanium or silicon; it is primarily used as a switching device [7] [13].


DIODE DETECTOR

A demodulator that uses one or more diodes to provide a rectified output with an average value that is proportional to the original modulation [12] [18].


DIPOLE

A common type of half-wave antenna made from a straight piece of wire cut in half. Each half operates at a quarter wavelength of the output [10].


DIRECT CURRENT

An electric current that flows in one direction only [1].

DIRECT SHORT

Same as SHORT CIRCUIT [3].

DIRECTIONAL ANTENNA

An antenna that radiates most effectively in only one direction [18].

DIRECTIONAL COUPLER

A device that samples the energy traveling in a waveguide in one direction
only [11].


DIRECTIVITY

The ability of an antenna to radiate or receive more energy in some directions than in others. The degree of sharpness of the antenna beam [10] [11] [18].


DIRECTLY HEATED CATHODE

A wire, or filament, designed to emit the electrons that flow from
cathode to plate. The filament is designed so that a current is passed through it; the current heats the filament to the point where electrons are emitted [6].


DIRECTOR

The parasitic element of an array that reinforces energy coming from the driver element [10].


DISCRETE COMPONENTS

Individual transistors, diodes, resistors, capacitors, and inductors [14].

DISCRIMINATOR

A circuit in which amplitude variations are derived in response to phase or frequency variations [18].


DISPERSION

The refraction of light waves that causes the different frequencies to bend at slightly different angles [10].


DISPLACEMENT CURRENT

The current that appears to flow through a capacitor [2].

DISTILLED WATER

Water that has been purified through a process of evaporation and condensation [18].


DISTORTION

Any unwanted change between an input signal and output signal [6] [8].

DISTRIBUTED CONSTANTS

The constants of inductance, capacitance, and resistance in a transmission line. They are spread along the entire length of the line and cannot be distinguished
separately [10].


DISTRIBUTIVE LAW

In Boolean algebra the law which states that if a group of terms connected by like operators contains the same variable, the variable may be removed from the terms and associated with them by the appropriate sign of operation (for example, A(B + C) = AB + AC) [13].


DOMAIN THEORY

A theory of magnetism based upon the electron-spin principle. Spinning electrons have a magnetic field. If more electrons spin in one direction than another, the atom is magnetized [1].


DOMINANT MODE

The easiest mode to produce in a waveguide, and the most efficient mode in terms of energy transfer [11].


DONOR

An impurity that can make a semiconductor material an N-type by donating extra "free" electrons to the conduction band [7].


DONOR IMPURITY

See PENTAVALENT IMPURITY [7].

DOORKNOB TUBE

An electron tube that is similar to the acorn tube but larger. The doorknob tube is designed to operate, at high power, in the uhf frequencies [6].


DOPING

The process of adding impurities to semiconductor crystals to increase the number of free charges that can be moved by an external, applied voltage. Doping produces N-type or P-type material [7] [14].


DOPPLER EFFECT

(1) The apparent change in frequency or pitch when a sound source moves either toward or away from a listener [10]. (2) In radar, the change in frequency of a received signal caused by the relative motion between the radar and the target [18].


DOPPLER FREQUENCY

The difference between transmitted and reflected frequencies; caused by the
Doppler effect [18].


DOUBLE NEGATIVE LAW

In Boolean algebra, the law which states that the complement of a
complement is the equivalent of the original term [13].


DOUBLE RECEIVER

A fine and coarse synchro receiver enclosed in a common housing with a two-
shaft output (one shaft inside the other) [15].


DOUBLE-MODING

In a transmitter output tube, the abrupt and random change from one frequency to another [18].


DOUBLET

Another name for the dipole antenna [10].

DOUBLING UP

This is a type of two-equipment installation where one unit can be substituted for another in the event of failure [17].


DOWN LINK

The frequency used to transmit an amplified signal from a satellite or other craft back to earth [17].


DRIFT SPACE

In an electron, a region free of external fields in which relative electron position depends on velocity [11].


DRIVEN ARRAY

An array in which all of the elements are driven [10].

DRIVEN ELEMENT

The element of an antenna connected directly to the transmission line [10].

DRIVER

The final stage of amplification [8].

DRUM-TYPE ARMATURE

An efficient, popular type of armature designed so that the entire length of
the winding is cutting the field at all times. Most wound armatures are of this type [5].


DRY CELL

An electrical cell in which the electrolyte is not a liquid. In most dry cells the electrolyte is in the form of a paste [1].


DRY-AIR SYSTEM

Provides dehumidified air for electronic equipment that is moisture critical [18].

DUAL IN-LINE PACKAGE (DIP)

IC package having two parallel rows of preformed leads [14].

DUAL-GATE MOSFET

A two-gate MOSFET in which either gate can control the conductor
independently, a fact which makes this MOSFET very versatile [7].


DUCTILE

Easily drawn out (as to form filaments or wires) [4].

DUCTING

Trapping of an RF wave between two layers of the earth's atmosphere or between an atmospheric layer and the earth [18].


DUMMY ANTENNA

See DUMMY LOAD [16].

DUMMY LOAD

A dissipative but nonradiating device that has the impedance characteristics of an antenna or transmission line. Also called ARTIFICIAL LOAD [11] [16] [17].


DUPLEXER

A radar device that switches the antenna from the transmitter to the receiver and vice versa [18].


DUTY CYCLE

In a transmitter, ratio of time on to time off [12] [18].

DYNAMIC MICROPHONE

A device in which sound waves move a coil of fine wire that is mounted on
the back of a diaphragm and located in the magnetic field of a permanent magnet [12].



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